I was growing H sigitalis well and decided to lift it to a higher level to get more light........unfortunately it missed out on a few waterings, and I lost it...so I would say keep it moist, but I seem to remember Carol keeps hers dry ??? Carol ?
H buotii does not like to dry out, and the flowers are really lovely and a good size.....here's a pic of mine in bloom...one of my favourites with a lovely scent

Dominic, Is the colour of your buotii true in that picture?. Mine is going to bloom and it's more yellow than pink. I love this hoya tho whatever the colour. I'll try and put a picture of my plant because when it blooms it's covered in umbels.

Yes, Dorothy...it's a salmon pink color, I've been asked that before by people who have a yellower version....Prob my growing conditions..wasnt bought as a 'pink' variety, or anything like that. To me it has a smell somewhere between peach and salmon..........of the fishy variety.....Strange, but nice.
Another photo of it

When I upload a photo, I use photoshop to try and get the color as true as poss, because they dont always photograph true to color.......my all time favourite was this H mac 'Rainforest', which really did flower this dark for me......Amazing plant...
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I have an IML 0016 or 0017 which is supposed to be darker...but I'm struggling with that one..maybe one day...:))

Steven,
I have my H.sigilatis under the lights right now, but either under lights or in the greenhouse or outside, I don't let it go as dry as I do alot of the other Hoya's. And in Hot weather more water. The foliage is gorgeous but even more so in high light.
H. boutii also, I got it very late last fall as a cutting and it's rooted and growing like a weed. I let it dry out a little more than H.sigilatis. This pic was taken when it had been hanging on the porch getting very bright light but no hot
sun. I think your going to really enjoy these two !

....H. sigallatis's happiness eluded me for the LONGEST time... I managed to murder quite a few...they rotted out. This one is happy in very high light, very warm (it swings from the top of the greenhouse), very lose 'soil' (actually about 60% hydroton and the rest bark chips and perlite) and it gets watered when it is DRY (when everyone else gets it...about every 5 days these days...3-4 for the smaller pots) and if it's hot/dry weather I spray it down every day with a hose. No "misting" my guys....when it rains in the tropics it strangles frogs!!!!!